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add ascending to IterableExtension.sortedBy #731

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add ascending to IterableExtension.sortedBy #731

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fd91b67
add `ascending` to IterableExtension.sortedBy
arthurbcd Dec 6, 2024
c63dff2
Improve compare function in sortedBy extension
arthurbcd Nov 10, 2025
bdc7f6c
Merge branch 'main' into main
arthurbcd Nov 10, 2025
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13 changes: 9 additions & 4 deletions pkgs/collection/lib/src/iterable_extensions.dart
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Original file line number Diff line number Diff line change
Expand Up @@ -6,7 +6,6 @@ import 'dart:math' show Random;

import 'algorithms.dart';
import 'functions.dart' as functions;
import 'utils.dart';

/// Extensions that apply to all iterables.
///
Expand Down Expand Up @@ -71,10 +70,16 @@ extension IterableExtension<T> on Iterable<T> {
/// Creates a sorted list of the elements of the iterable.
///
/// The elements are ordered by the natural ordering of the
/// property [keyOf] of the element.
List<T> sortedBy<K extends Comparable<K>>(K Function(T element) keyOf) {
/// [keyOf] property when [ascending] is `true` or reverse ordering
/// when [ascending] is `false`.
List<T> sortedBy<K extends Comparable<K>>(
K Function(T element) keyOf, {
bool ascending = true,
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@lrhn lrhn Apr 23, 2025

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I think I would prefer to name it descending, so the default is false.
Just because it's usually best to have "nothing" mean false.
Then it feels like you are opting in to the non-default behavior. Using ascending: false feels ... conflicted. You are opting out of the default behavior, but that doesn't directly say what it opts in to.

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@arthurbcd arthurbcd Nov 10, 2025

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I understand the concern about double negatives with ascending: false. However, I'd lean towards ascending: true in this case because:

  1. Flutter's DataTable already uses sortAscending: true as the default, and DataColumnSortCallback uses bool ascending in its signature
  2. In sorting contexts across Flutter/Dart, I feel developers would expect the ascending parameter

That said, I recognize the clarity benefit of descending: true for opt-in behavior. If you still prefer descending: false after considering these points, I'm happy to update it accordingly. :)

}) {
final compare =
ascending ? (K a, K b) => a.compareTo(b) : (K a, K b) => b.compareTo(a);
var elements = [...this];
mergeSortBy<T, K>(elements, keyOf, compareComparable);
mergeSortBy<T, K>(elements, keyOf, compare);
return elements;
}

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10 changes: 10 additions & 0 deletions pkgs/collection/test/extensions_test.dart
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Expand Up @@ -70,6 +70,16 @@ void main() {
test('multiple', () {
expect(iterable(<int>[3, 20, 100]).sortedBy(toString), [100, 20, 3]);
});
test('multiple ascending', () {
expect(
iterable(<int>[3, 20, 100]).sortedBy(toString, ascending: true),
[100, 20, 3]);
});
test('multiple descending', () {
expect(
iterable(<int>[3, 20, 100]).sortedBy(toString, ascending: false),
[3, 20, 100]);
});
});
group('.sortedByCompare', () {
test('empty', () {
Expand Down
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